The present invention relates to a flexible membrane device that assumes the gap between two unlike sized pipes or tubes, where as the smaller of the two pipes is inserted vertically downward into the larger pipe and the flexible membrane prevents egress of internal fluids outside of the pipe confines if, for example, the pipes become full and fluid pressure occurs, or if fluid flow direction is reversed and velocity pressure occurs. More specifically, the present invention relates to roof draining systems that are adapted to be retrofitted into existing roof drain pipes usually at the time the roof is re-roofed. It should be understood, however, that the principles of the present invention can be utilized in new construction as well as in re-roofing systems. Generally, re-roofing drain systems include an outlet pipe having an upper flange mountable on roof insulation or roofing material. In some cases, the outlet pipe is sealed to the interior of the drain pipe by a pre-compressed foam material but other forms of seals described below have been used as well. A rib on the top of this flange sometimes mates with a groove on a cast aluminum gravel guard collar, which in essence is a ring element that provides a flashing lock to the flange with a roofing membrane clamped between the collar and the flange. The flange and the outlet tube are frequently available in stainless steel, PVC, aluminum or high temperature ABS and are available to accommodate but not limited to 2, 3, 4, 5, and 6 inch drains. The drain can be installed on an existing roof top without special tools and the hardware is frequently stainless steel. A straining system is sometimes provided on top of the clamping ring that includes a one-piece dome-type strainer.
When re-roofing is necessary, the original drain systems must be replaced in part because of rusted bolts and frequently the gravel ring breaks upon removal.
The present invention relates particularly to the methodology for sealing the outlet pipe to the interior of the drain pipe. This is an essential function in re-roof drain systems because backup water pressure from the drain pipe, if it escapes around the outlet pipe, will find its way to an area underneath the roof and into the building interior.
One system for sealing designed by the assignee of the present invention is a pre-compressed foam tape glued to the exterior of the outlet pipe. Just prior to installation of the outlet pipe, the installer removes the pre-compressed tape permitting the foam to expand as the outlet pipe is inserted into the existing drain pipe. This system has been found satisfactory but in some cases, insertion into the drain pipe has been found difficult and if the outer diameter of the pre-compressed foam is decreased to facilitate insertion into the drain pipe, some leakage will occur particularly upon backup water pressures of 50 column feet or more. Immediately upon removing the tape and prior to the full expansion of the foam, the smaller pipe is inserted and positioned in the larger pipe. The foam continues to expand at a rate effected by ambient temperature and other conditions until restricted by the void between the two pipes. This system has been found satisfactory in some cases, but insertion into the drain pipe has been found difficult based on installer skill or speed, and ambient conditions. Unlike the present invention, this type seal may experience some leakage around the wrapped joint or through the foam material when subjected to fluid pressure.
Other roofing systems include one-piece rubber seals that are somewhat more relevant to the present invention than the above-described assignee""s expandable foam system. One such seal is manufactured by Zurn Industries, Inc. of Pittsburgh, Pa., and it includes a one-piece elastomeric seal having a plurality of thin annular rings there-around that are integral with the seal.
Another re-roofing seal is made by Thaler Metal Industries, Inc., Model No. M-22, and this system includes a one-piece elastomeric seal constructed of EPDM Posiseal that is similar in construction to the Zurn seal described above.
U-Flow, Inc. has a mechanical compression seal adapter positioned immediately below the roof deck. This annular seal, Model Nos. UF-3 to UF-6 include a heavy annular section with an even heavier lower annular seal portion that engages the inside diameter of the drain pipe. This seal is largely inflexible. This seal requires axial compression with a plurality of threaded members after insertion into the drain pipe to effect radial expansion and sealing against the drain pipe, making it very difficult to operate and unpredictable. This product has a U.S. Pat. Nos. 4,505,499 and 4,799,713.
Marathon Roofing Products, Inc. of Buffalo, N.Y., has a U.S. Pat. No. 4,759,163, on a one-piece elastomeric seal that must be expanded in a similar manner to the U-Flow seal described above.
The RAC Roof Accessories Company, Inc., U.S. Pat. No. 5,141,633, includes a rubber seal to seal against back flow, constructed of a one-piece urethane member that extends below a frusto-conical lower end of the outlet pipe in the system that assists in urging the seal outwardly against the drain pipe. This seal is essentially just a thin annular ring except for the lower frusto-conical portion.
Other prior art utilizes a one-piece elastomeric seal having a plurality of thin annular rings there-around that are integral with the seal. One such manufacturer is Zurn Industries, Inc. of Pittsburgh, Pa. Another re-roofing seal is made by Thaler Metal Industries, Inc., Model No. M-22, and this system includes a one-piece elastomeric seal constructed of EPDM Posiseal that is similar in construction to the Zurn seal described above. Unlike the present invention, this type seal does not account for misalignment and could leak when witnessing high fluid pressure.
In all cases, prior art has shortcomings since each has its own unique problem with assembly methods, installer skill or tool requirements, self-alignment, and their inability to withstand high pressure when the drain becomes full and/or flow is reversed.
In short, the above prior art systems have been found to be both difficult to insert into the existing drain pipe and include difficult and complicated mechanisms for expanding the seal, and have not been found under testing to prevent leakage at backup pressures in excess of 50 column feet.
For the above reasons, it is a primary object of the present invention to provide a roof drain system with a seal for sealing the drain system to the drain pipe interior and eliminate the many problems noted above in prior art seals.
In accordance with the present invention, a roof drain system is provided for existing roofs or new construction including a flanged outlet pipe for insertion into the roof drain pipe with the flange mounted on top of the roof. A water straining system is mounted on top of the flange. The outlet pipe is sealed to the interior of the drain pipe by a one-piece rubber molding seal that flexes to easily slide into the drain pipe and withstands high backup water pressures from the drain pipe without leaking. The seal has a Shore A durometer in the range of 30 to 95 and has an annular portion engaging the outer surface of the outlet pipe and an integral flange portion extending outwardly and downwardly from the upper end of the annular portion that seals the inner surface of the drain pipe.
The present seal eliminates the necessity for complicated seal expanding components noted above in many of the prior art drain pipe sealing devices in roof drain systems. Toward these ends, the present seal includes the annular portion noted above that has a radial flange that engages the extreme lower end of the outlet pipe and this axially locates the seal with respect to the outlet pipe and furthermore resists upward movement of the seal relative to the outlet pipe upon backup water pressure in the drain pipe.
The seal is constructed of rubber but could also be constructed of other materials such as poly-urethane. It is a one-piece molding and the flange is spheroidal in configuration and has a radius of about 1.5 inches about a center spaced about 0.535 inches from the axial center line of the seal. In the 4 inch seal, i.e.; designed to seal against a 4 inch diameter drain pipe, the flange is flexible and forms a hydrostatic pocket between itself and the outer surface of the seal annular portion. Water pressure in this pocket serves to expand the frusto-spheroidal flange into engagement with the drain pipe interior as backup water pressure increases, providing a very effective seal and eliminating any seal leakage at backup pressures as high as 50 column feet or more.
Other objects and advantages of the present invention will appear more clearly from the following detailed description.